| Objective:1.Establish a finite element model of digital simulation after percutaneous full-endoscopic anterior transcorporeal cervical discectomy(PEATCD).2.To analyze the difference of motion of finite element model before and after operation during flexion,extension,lateral bending and axial rotation.3.Biomechanical differences between damaged and intact vertebrae were analyzed during flexion,dorsiflexion,lateral bending and axial rotation.Methods: The geometric data of cervical spine were collected from No.2 Chinese Visual Human dataset.A finite element model of C2-T1 spine of normal Chinese was established as a pre-operative model,and a channel on C4 vertebral body was established as a post-operative model.1.Preloading 100 N to simulate the human head weight on the preoperative and post-operative models respectively,then loading 2Nm pure torque on the upper surface of the model along the direction of flexion,back extension,lateral bending and axial rotation to simulate the physiological activities of the cervical spine.The range of motion of C3/4intervertebral space and the whole cervical spine were collected on the preoperative and post-operative models,and the influence of operation on cervical stability was analyzed.2.ABAQUS was used to apply 100 N head gravity and 2Nm pure torque to preoperative and postoperative models to simulate cervical spine’s movements of flexion,dorsal extension,lateral bending and axial rotation.The stress distributions of cortical bone and spongy bone in preoperative and postoperative models were compared.3.The upper surface of the cervical spine model was loaded with 0.2Nm pure torsion step by step to simulate the cervical flexion movement,and the maximum stress of cortical bone at the opening of the C4 vertebral channel corresponding to each level of torsion was obtained.Two groups of data were imported into SPSS 20.0 for linear-regression analysis.Result: Comparisons of cervical spine motion before and after operation under the loading of 100 N head gravity and 2Nm pure torque: during flexion motion,the C3/4segment motion was 10.303 degrees,and after operation,the C3/4 segment motion was11.292 degrees,which increased by 0.991 degrees compared with that before operation.The overall range of motion of the model was 48.890 degrees before operation and 49.855 degrees after operation,which increased by 1.046 degrees after operation.The range of motion of C3/4 segment was 5.546 degrees before operation and 6.31 degrees after operation,which increased by 0.764 degrees after operation.The overall motion of the model was 27.771 degrees before operation and 28.539 degrees after operation,which increased by 0.768 degrees after operation.The motion of C3/4 segment was 5.52 degrees before operation and 5.702 degrees after operation,which increased by 0.182 degrees after operation.The overall motion of the model was 31.959 degrees before operation,32.130 degrees after operation and 0.171 degrees after operation.The motion of C3/4 segment was6.65 degrees before operation,7.067 degrees after operation and 0.417 degrees after operation.The activity of the whole model was 34.895 degrees before operation and35.383 degrees after operation,which was 0.488 degrees higher than that before operation.During the flexion,extension,rotation and lateral curvature of the cervical spine model after operation,the cervical spine activity changed slightly compared with that before operation.There were no fractures and collapses in the cervical spine during the exercise,and the stability of the cervical spine was not destroyed.The influence of surgery on the stress distribution of cortical bone of C4 vertebra where the channel is located: during cervical flexion,the compressive stress of cortical bone of C4 vertebra mainly concentrates in the middle of anterior wall of C4 vertebra,and after operation,the compressive stress of cortical bone of C4 vertebra mainly concentrates in the middle of both sides of the channel’s entrance;during dorsal extension,the compressive stress of cortical bone of C4 vertebra before operation mainly concentrates in the pedicle of vertebra,and the compressive stress of C4 Comparing with the preoperative model,stress concentration was also observed at the opening of the channel besides thepedicle of the vertebral arch.During the lateral bending movement,the compressive stress of cortical bone of C4 vertebrae was mainly concentrated at the pedicle of the vertebral arch before operation,but there was no significant change in the position of compressive stress concentration after operation.During the axial rotation,the compressive stress of cortical bone of C4 vertebrae before operation was concentrated at the pedicle of the vertebral arch,and the area of compressive stress Similarly,the cortical bone stress at the upper edge of the opening increased significantly.The influence of operation on the compressive stress distribution of spongy bone in C4 vertebrae: during flexion,the compressive stress of spongy bone concentrates in the central region of vertebral body before operation,and after operation,the compressive stress of spongy bone concentrates in the channel wall;during back extension,the compressive stress of spongy bone in preoperative model concentrates in the middle of vertebral body,and after operation,the compressive stress of spongy bone concentrates in the entrance of the channel;during lateral bending,the compressive stress of spongy bone The compressive stress of posterior spongy bone concentrates on the pedicle and hook of vertebral body.The compressive stress of internal spongy bone of vertebral body does not change significantly before and after operation.The compressive stress of C4 spongy bone concentrates on the lateral mass of C4 vertebral body before rotation exercise,and the compressive stress of C4 spongy bone concentrates on the channel wall and lateral mass after operation.When the model was loaded with 2Nm torque to simulate flexion,dorsiflexion,lateral bending and rotation,no fracture occurred in the stress concentration area of the model C4 vertebrae,and the stability of the model C4 vertebrae was not destroyed after operation.With the pure torsion applied on the surface of cervical spine model step by step as the independent variable,and the cortical bone stress around the entrance of vertebral channel as the dependent variable,the scatter statistical chart shows that the relationship between them is linear.Using linear regression equation analysis and F test,it is concluded that the loading torque is positively correlated with the cortical bone stress around the entrance of vertebral channel after surgery,and the greater the applied torsion,the better therelationship between them.The greater the force,the more pure torque applied,the greater the number of cervical spine flexion.Therefore,the greater the flexion activity of cervical spine,the greater the stress of cortical bone around the opening of the vertebral channel.Conclusion:1.The finite element model of cervical spine based on Chinese visible human dataset simulates the operation mode of PEATCD.It is feasible to use this model to analyze the biomechanical stability of cervical spine after operation,and can be used for the follow-up finite element analysis of PEATCD.2.The range of motion of the model after operation was smaller than that before operation,and the operation did not cause cervical spine instability.No fracture or collapse was found in the cervical spine 4 during flexion,dorsal extension and rotation.In the normal range of physiological movement of cervical spine,the operation did not destroy the stability of cervical spine,and the operation was safe and reliable.3.Applying 0.2Nm pure torsion step by step on the upper surface of cervical spine model makes the cervical spine move more and more in flexion direction,which leads to the increasing stress of cortex around cervical vertebral passage 4 after operation.Postoperative patients are advised to avoid excessive cervical flexion and wear neck braces if necessary to reduce the risk of cortical bone fracture around the access. |
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